1. Field of the Invention
The present invention relates to a mute switch, used in audio circuits to reduce the audio level to zero, and more particularly to a mute switch that can operate at low supply voltages.
2. Description of the Related Art
Mute switches are typically placed in the path between an audio input node and audio output node such that that path can be “disconnected” to reduce the level of the audio output signal at the audio output node to zero when required. The mute switch is controlled by a mute control signal.
An existing mute switch is discussed in more detail later with reference to FIG. 1, but takes the form of a simple MOS transistor. There are two difficulties with such a switch. The first is that the voltage level of the mute control signal that is required to control the switch can exceed the voltage supply level for low voltage applications. Clearly this is unsatisfactory. Another difficulty is that the DC bias level of the audio output signal will alter depending on the status of the mute control signal and the resulting state of the mute control switch. This can introduce annoying and possibly damaging “pops and clicks” which can be heard when the switch is used.